Add oil and long time no see: when Chinglish enters real English
A phrase can begin as literal translation, pidgin contact, or bilingual play, then become so useful that people keep it.
From error to expression
Add oil carries the energy of 加油: encouragement, effort, and cheering someone on. Long time no see is widely understood in English, even if its exact origin is debated.
The interesting question is not whether the grammar is standard. It is why the phrase carries a feeling that standard translation may lose.
How to classify Chinglish
It helps to separate translation mistakes, China English, internet hybrid language, and expressions that have already travelled into broader English.